Since the establishment of the 3rd Generation Partnership Project Release7 (3GPP Release7) standard system, the policy and charging function is realized by a Policy and Charging Control (PCC) framework. The PCC framework is a functional framework applicable to multiple access technologies, for example, the PCC framework is applicable to a Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), Global System for Mobile Communication (GSM)/Enhanced Data Rate for GSM Evolution (EDGE) radio access network, an Interworking Wireless Local Area Network (I-WLAN) and an Evolved Packet System (EPS), etc.
The PCC mainly realizes two functions, that is, a policy control function and a charging function. FIG. 1 is a schematic diagram of a PCC framework in existing Rel-11. Hereinafter, each logical function and the interface function thereof in the PCC framework shown in FIG. 1 are described. As shown in FIG. 1:
An Application Function (AF) is configured to provide an access point of traffic application, wherein network resources used by the traffic application need to be processed with dynamical policy control. When parameter negotiation is conducted on a traffic plane, the AF transmits related traffic information to the PCRF. If the traffic information is consistent with the policy of the PCRF, the PCRF accepts the negotiation; otherwise, the PCRF rejects the negotiation, and provides traffic parameters acceptable by the PCRF during feedback. Subsequently, the AF may return these parameters to User Equipment (UE), wherein the interface between the AF and the PCRF is an Rx interface.
The PCRF is the core of the PCC and is responsible for establishing policy and charging rules. The PCRF provides network control rules based on a traffic data flow, wherein the network control includes detection, gating control, Quality of Service (QoS) control of the traffic data flow, and charging based on the data flow. The PCRF sends the policy and charging rules established by the PCRF itself to a Policy and Charging Enforcement Function (PCEF) to execute. Meanwhile, the PCRF also needs to guarantee the consistency between the rules and the subscription information of a user. The basis for the PCRF to establish the policy and charging rules includes: obtaining traffic related information from the AF, obtaining user subscription information of policy and charging control associated with policy control and charging from a Subscription Profile Repository (SPR), and obtaining bearer related network information from the PCEF.
The PCEF is generally located inside a Gate-Way (GW) and is used for executing the policy and charging rules established by the PCRF on a bearer plane. The PCEF detects traffic data flows according to a traffic data flow filter in the rules sent by the PCRF, thereby executing the policy and charging rules established by the PCRF for the traffic data flow. When a bearer is established, the PCEF allocates resources according to the rules sent by the PCRF and performs gating control according to the information provided by the AF. Meanwhile, the PCEF triggers the report of events occurring on a bearer network according to an event subscribed by the PCRF. According to the charging rules sent by the PCRF, the PCEF executes a corresponding traffic data flow charging operation, wherein the charging can be online charging or offline charging. If in the online charging, the PCEF needs to perform credit management together with an Online Charging System (OCS); if in the offline charging, the PCEF exchanges related charging information with an Offline Charging System (OFCS). The interface between the PCEF and the PCRF is a Gx interface; the interface between the PCEF and the OCS is a Gy interface; and the interface between the PCEF and the OFCS is a Gz interface. The PCEF can also have the TDF. The PCEF can perform application detection and policy execution (for example, gating control, redirection and bandwidth limit) according to local configurations or PCC rules containing an application detection and control policy distributed by the PCRF. The PCEF is generally located on a network gateway, such as a Packet Data Network Gateway (PDN-GW) of EPS, a General Packet Radio Service (GPRS) Gateway Support Node (GGSN), and a Packet Data Gateway (PDG) in an Interworking Wireless Local Area Network (I-WLAN).
Of course, the TDF can also be deployed separately; at this time, the TDF is connected with the PCRF through an Sd interface; the TDF can perform application detection and policy execution according to an Application Detection and Control (ADC) rule preconfigured or distributed by the PCRF.
A Bearer Binding and Event Reporting Function (BBERF) is generally located in an access network gateway. For example, when the user equipment accesses the EPS through an E-UTRAN and Proxy Mobile Internet Protocol version6 (PMIPv6) is applied between an S-GW and a P-GW, the BBERF exists in the S-GW. When the user equipment accesses the EPS through a trusted non-3GPP access network, the BBERF also exists in the trusted non-3GPP access gateway.
The SPR stores the user subscription information of policy and charging control associated with policy control and charging. The interface between the SPR and the PCRF is an Sp interface. The OCS and the PCEF together accomplish the user credit control and management in the online charging mode. The OFCS and the PCEF together accomplish the charging operation in the offline charging mode.
FIG. 2 is a flowchart of establishing a TDF session between a TDF and a PCRF in an existing IP-CAN session process, wherein the TDF applies a non-requested report mode. As shown in FIG. 2, the process includes Step S201 to Step S214:
Step S201: During the process of UE requesting establishment of an IP-CAN session, a gateway where a PCEF is located receives an IP-CAN session establishment request message, wherein a user identifier and a PDN identifier of the PDN network which the user requests to access are carried in the IP-CAN session establishment request message.
Step S202: The PCEF sends an IP-CAN session establishment indication message to the PCRF, wherein the user identifier, the PDN identifier and an IPv6 address prefix allocated for the UE are carried in the IP-CAN session establishment indication message.
Step S203: After judging that there is no subscription information of the user according to the user identifier, the PCRF sends a subscription document request to an SPR and makes the subscription document request carry the user identifier and the PDN identifier.
Step S204: The SPR returns corresponding user subscription information (through a subscription document response) according to the user identifier and the PDN identifier.
Step S205: The PCRF makes a policy decision (including establishing PCC rules and event triggers) according to returned user subscription information, network policy, UE access information and the like.
Step S206: The PCRF sends an IP-CAN session establishment acknowledgement message to the PCEF, wherein the PCC rules and event triggers are carried in the IP-CAN session establishment acknowledgement message.
Step S207: The PCEF installs the policy; the gateway where the PCEF is located returns an IP-CAN session establishment response to the UE, wherein the IPv6 address prefix is carried in the IP-CAN session establishment response.
Step S208: If the network supports a dual stack, the gateway where the PCEF is located or another external network element further allocates an IPv4 address according to a request from the UE.
Step S209: The PCEF sends an IP-CAN session modification indication to the PCRF, wherein the IPv4 address is carried in the IP-CAN session modification indication to inform the PCRF that the IP-CAN session has a new IPv4 address.
Step S210: The PCRF returns the acknowledgement message of the IP-CAN session modification indication to the PCEF.
Through the processes shown in FIG. 2, the UE can construct an IPv6 address according to the IPv6 address prefix and access a traffic using the IPv6 address and the IPv4 address.
Step S211: The TDF detects the data flow flowing therethrough according to a preconfigured ADC rule. When detecting that one application of the IPv4 address (which is allocated in Step S208) needs to be reported, the TDF sends a TDF session establishment message to the PCRF (since the TDF session corresponding to the IPv4 is not established), wherein the IPv4 address and the detected application identifier are carried in the TDF session establishment message. If flow description information of the detected application can be derived, the TDF makes the establishment message carry the flow description information. The PCRF links the TDF session with the IP-CAN session according to the IPv4 address obtained from the PCEF and the IPv4 address obtained from the TDF. The PCRF updates the policy associated with the IP-CAN session according to the application information reported by the TDF.
Step S212: The PCRF returns the acknowledgement message of the TDF session establishment message.
Step S213: Before receiving the message from Step S212, if the TDF detects that one application of the IPv6 address (which is constructed by the UE according to the IPv6 address prefix in Step S207) needs to be reported, the TDF sends a TDF session establishment message to the PCRF (since the TDF session corresponding to the IPv6 is not established), wherein the IPv6 address and the detected application identifier are carried in the TDF session establishment message. If flow description information of the detected application can be derived, the TDF makes the establishment message carry the flow description information. The PCRF links the TDF session with the IP-CAN session according to the IPv6 address obtained from the PCEF and the IPv6 address obtained from the TDF. The PCRF updates the policy associated with the IP-CAN session according to the application information reported by the TDF.
Step S214: The PCRF returns the acknowledgement message of the TDF session establishment message.
The scenarios executed in above steps are different, thus the TDF locations are different. For the home routing roaming scenario, the TDF is located at home to establish a TDF session with the H-PCRF; for local breakout roaming scenario, the TDF is located at visited to establish a TDF with the V-PCRF.
Through the above processes, the two TDF sessions are linked to one IP-CAN at the same time, and the TDF reports the application related with the IPv4 address and the application related with the IPv6 address to the PCRF through the two TDF sessions, respectively. Then, since the IPv4 address can be applied for and released dynamically, if the UE releases the IPv4 address, the network allocates the same IPv4 address to other UE. According to the relevant technology, the TDF can report the application information through the TDF session established for the UE in the above processes, thereby resulting in the PCRF making a wrong policy.
Furthermore, if the network also supports the IPv6 prefix delegation (i.e., the network supports the allocation of a short prefix), when the UE constructs two or more IPv6 addresses according to the IPv6 prefix and accesses the traffic, since the TDF is unable to determine whether these IPv6 addresses belong to the same IP-CAN session (if the TDF is unable to obtain the IPv6 prefix allocated by the network for the UE, the TDF assumes that the IPv6 addresses, of which any previous 64 bits are different, are from different UE), an IP-CAN session is also present, while the TDF session associated with an IPv4 address and the TDF session associated with one or more IPv6 addresses are present. If the UE releases the IPv4 address, the network allocates the same IPv4 address to other UE. According to the relevant technology, the TD can report the application information through the TDF session established for the UE in the above processes, thereby resulting in the PCRF formulating a wrong policy.
In fact, for the IP-CAN session supporting the dual stack, the TDF session related with one IPv4 address exists in the IP-CAN session. If the UE releases the IPv4 address, the network allocates the same IPv4 address to other UE. According to the relevant technology, the TDF can report the application information through the TDF session established for the UE in the above processes, thereby resulting in the PCRF making a wrong policy.